Rust: What is the difference between Option and Result in Rust?

Option — value or none. Result — success or error.

Option:

• Value present or absent.
• Some(T) or None.
• For optional values.
• No error information.

1fn find(haystack: &str, needle: char) -> Option<usize> {
2    for (i, c) in haystack.chars().enumerate() {
3        if c == needle {
4            return Some(i);
5        }
6    }
7    None
8}

Result:

• Success or failure.
• Ok(T) or Err(E).
• For operations that can fail.
• Contains error info.

1use std::fs::File;
2
3fn open_file(path: &str) -> Result<File, std::io::Error> {
4    File::open(path)
5}

Key differences:

• Option — value or none.
• Result — success or error.
• Option — no error info.
• Result — has error info.